Corrosion inhibiting aqueous amine dispersion emulsified with an ethoxylated amide



United States Patent 3,418,253 CORROSION INHIBITING AQUEOUS AMINEDISPERSION EMULSIFIED WITH AN ETHOXY- LATED AMIDE Ronald M. Silverstein,Parsippany, N.J., and Chester A. Bishof, Glenside, Pa., assignors toBetz Laboratories. Inc., Philadelphia, Pa., a corporation ofPennsylvania No Drawing. Filed Oct. 23, 1965, Ser. No. 504,072 9 Claims.(Cl. 252-392) ABSTRACT OF THE DISCLOSURE The present invention concernsmethods and materials for inhibiting the corrosion of metal surfacescontacted by steam or steam condensate in which an aqueous dispersion ofa straight chain aliphatic hydrocarbon primary amine emulsified with anethoxylated amide is dispersed in the steam or steam condensate. Typicalof the amines and amides employed are octadecylamine and ethoxylatedoctadecylamide.

The present invention relates to methods for dispersing fatty amines inaqeuous systems, and particularly to methods for dispersing fatty aminesin the steam and/or steam condensate contained by a boiler system.

It has previously been found that the corrosion which is incurred by thecontact of steam and/or steam condensate with the metal components of aboiler system may be inhibited or eliminated by incorporating smallquantities of a fatty amine in the corrosive fluid. It is believed thatdespite the small quantities of amine employed, a protective filmresistant to penetration by corrosive elements is formed upon the metalsurfaces. Such methods are disclosed by U.S. Patent 2,460,259, toKahler. HOW- ever, the fact that the amines which provide the desiredcorrosion inhibition are solids possessing limited solubility anddispersibility has rendered their use difiicult. To overcome thesedifficulties a variety of techniques for converting the amine to anaqueous dispersion prior to its introduction to the boiler system havebeen devised. For example, as disclosed by U.S. Patent 2,712,531 toMaguire, the amines have been employed in the form of their salts, e.g.,octadecylamine acetate, which are generally more soluble anddispersible. However, the use of these amine salts has also causedproblems in that the release of the acid often causes the degradation ofthe amines with a consequent reduction in their corrosion inhibitingproperties, and an increase in the accumulation of fouling depositswithin the system. Furthermore, at those points of localized hightemperature which are common in a boiler system, the amine salt isdecomposed to form free amine and free acetic acid with a consequentincrease in the corrosive properties of the system. In addition, thesalt component of the amine salt does not contribute directly tocorrosion inhibition.

The use of emulsifiers in aiding the dispersing of the amines in apro-emulsion has also been employed by the prior art. For example, theuse of polyalkoxylated amines, polyamines, glycols and quaternaryamines, is disclosed by U.S. Patent 3,088,796 to Kahler, and U.S.Patents 2,882,171 and 2,956,889, to Denman. However, in the use of suchemulsifiers, the quantity of emulsifiers required is undesirably highand generally results in high costs. Furthermore, their use results inthe corporation of relatively large quantities of foreign material whichdo not directly contribute to corrosion inhibition within the boilersystem. In turn, the volatility of many of these emulsifiers isinadequate for their complete distribution within the steam.

A purpose of the present invention is the provision of improved methodsfor dispersing fatty amines within the steam and/ or condensate ofboiler systems.

A further object is the provision of aqueous dispersions of fatty amineswhich may be readily dispersed within the steam and/or condensate of aboiler system.

Another object is the provision of readily dispersible, stable aqueousemulsions of fatty amines which are further characterized by a desirablyhigh concentration of the fatty amine.

An additional object is the provision of ready dispersible, stableaqueous emulsions of fatty amines which are characterized by meltingpoints which are equal to, or higher than, the melting point of thefatty amine.

Another object is the provision of readily dispersible, stable aqueousemulsions of fatty amines, in which the cost of emulsification isreduce-d through the use of low cost additives.

Still another object is the provision of a method for the emulsificationof fatty amines.

Yet another object is the provision of boiler systems protected againstcorrosion by means of the distribution of a fatty amine-emulsifiersystem within the steam and/ or condensate of the boiler system.

Further purposes appear in the specification and claims.

The invention generally comprises stable aqueous emulsions of a fattyamine which may be readily dispersed within the steam and/ or condensateof a boiler system to yield substantial improvements in respect to thereduction of the corrosion which normally occurs in such a system.Further improvements in the nature of favorable ratios of corrosioninhibitorzemulsifier, desirable melting points, prevention of thedegradation of the corrosion inhibitor, avoidance of fouling deposits offoreign matter within the boiler system, and reduced costs,are alsoprovided.

The objects of the invention are achieved by means of the emulsificationof a primary amine corrosion inhibitor by means of an alkoxylated amideemulsifier, and the dispersion of the resultant aqueous emulsion withinthe steam and/or condensate of a boiler system.

The primary amines employed in the invention are water insoluble,straight chain aliphatic primary monoamines having a carbon chain lengthof between 10 to 24 carbon atoms. Typical examples are octadecylamine,laurylamine, stearylamine, myristylarnine, cetylamine, eicosylamine,behenylamine, and the like.

The polalkoxylated compounds employed as emulsifiers are alkoxylatedamides containing between -98 percent by weight of ethylene oxide andpossessing a long chain aliphatic radical containing between 10 to 24carbon atoms. Such amides have the general formula:

In which R is an aliphatic hydrocarbon radical having between 10 to '24carbon atoms, and x and y are integers having a value such that theethyleneoxy content of the compound is between 70 and 98 percent byweight.

Typical examples of such compounds are ethoxylated tallow, lauryl, coco,or oleyl amide. However, a preferred emulsifier is ethoxylated octadecylamide having the formula:

It should also be noted that admixtures of the above describedethoxylated amides are suitable for the purposes of the presentinvention.

The emulsions of the invention may be prepared by admixing the fattyamine and the ethoxylated amide in the desired proportions and heatingthe mixture with agitation at a temperature of between l30-300 F. untilcompletely melted, and blending the molten admixtures with hot water,e.g., 130180 F. The blending is preferably accompanied by agitationuntil the temperature of the blend has fallen below 130 F. The resultantemulsion, or dilutions thereof, may be directly fed to the steam and/orcondensate of a boiler.

While highly concentrated or very dilute emulsions may be prepared, forease of feeding emulsions containing less than 50 percent by weight ofsolids are preferred.

It should also be noted that in most cases satisfactory emulsions may beprepared by separately adding the fatty amine and the amide emulsifierto water heated to 160- 180 F. with agitation.

The fatty taminezemulsifier system preferably contains between 40 to 90parts by weight of the amine, and between 1 to 60 parts by weight of theemulsifier. While higher concentrations of the emulsifier yieldsatisfactory emulsions, the emulsifier is maintained at a low level inorder to avoid the introduction of unnecessary quantities of foreignmaterial, which do not contribute directly to corrosion inhibition, tothe boiler system.

The preparation of a preferred emulsion is disclosed by the followingexample.

Example 1 An emulsion was prepared from 95 parts by weight of tap waterand parts by weight of an admixture of 85 percent by weight ofoctadecylamine and percent by weight of an ethoxylated octadecyl amidecontaining 84 percent by weight of ethylene oxide. The amine and amide,both of which are solids, were heated to 215 F. with agitation and theheat and agitation were maintained until a smooth molten blend wasobtained. One half of the specified quantity of tap water heated to 170F. was then added with agitation, and the remaining heated water wasslowly added thereafter. Agitation was maintained until the temperatureof the emulsion had dropped to F.

The resultant emulsion (5 percent solids) was fed to the steam header ofa boiler and yielded a highly satisfactory degree of corrosioninhibition. In the feeding of this emulsion, the steam header was tappedand the emulsion was introduced under a pressure in excess of theinternal pressure of the system by means of a piston pump. Similartreatments in which the same emulsion was injected into condensatereturn lines also yielded a high degree of corrosion inhibition.

It should also be noted that in many instances the practice of thepresent invention may embody the feeding of the emulsions of theinvention to plural segments of the boiler system. For example, whilethe corrosion inhibitors are preferably fed to the steam header foroptimal distribution throughout the system, some systems may alsorequire supplemental feeding to the condensate return sections, orfeeding exclusively to the condensate return sections. At any rate, thefeeding of corrosion inhibitors to boiler systems is generally andspecifically known to those skilled in the art, and obviouslysusceptible to various feeding techniques.

Similarly, the effective levels of amine corrosion inhibitors are knownto those skilled in the art. The quantity of amine introduced within theboiler system is preferably 0.5 to 30 parts for each one million partsof steam and condensate to be treated. However, in some instances aslittle as 0.01 part and as much as 200 parts per million parts may beeffectively used.

T 0 demonstrate the quality of the emulsions which are achieved by theinvention despite the relatively small quantity of emulsifier employed,the following studies of such emulsions are provided. In the preparationof each of the emulsions discussed below, the amine emulsifier mixturewas heated to F. and the resulting molten liquid was agitated as it wasallowed to cool. The admixtures were then dispersed in water heated toF. and the resultant emulsions were permitted to stand for 24 hours atroom temperature. At the end of the 24 hour period evaluations wereconducted in which an emulsion which was visibly homogeneous was ratedat Good, those exhibiting very slight non-uniformity were consideredFair, and those which demonstrated appreciable non-uniformity orcomplete separation of the solids were deemed Poor.

The data provided by Table 1 demonstrates the stability of emulsionsprepared in accordance with the invention, in which as little as 3percent by weight of the emulsifier is employed in emulsions containingas little as 0.5 percent by weight of the amine-emulsifier combination.

TABLE 1 Ethylene Solids Quality Nature of Amine and Quantity Nature ofAmide and Quantity Oxide Content Present in of (Percent by weight)(Percent by weight) of Emulsifier Emulsion Emul- (Percent by (Percent bysion weight) weight) Mixed Amines, 70.- Ethoxylated Laurylamide, 30. 91.7 0. 5 Good. 0 do 91. 7 8. 0 Do. Mixed Amines, 90.- EthoxylatedLaurylamide, 10 91. 7 0.5 Do. o...--- 91.7 8.0 Do. Mixed Amines} 97Ethoxylated Laurylamide, 3 91. 7 0.5 Do. o do 91. 7 8. 0 Fair MlxedAm1nes, 70.- Ethoxylated Tallow Amide, 30 88. 5 0. 5 Good. o.. do 88. 58. 0 Do. Mixed Amines, 90 Ethoxylated Tallow Amide, 1 88. 5 0.5 Do. Do.do 88.5 8.0 Do. Mixed Amines, 97 Ethoxylated Tallow Amide, 3 88.5 0. 5Do. Do.... w do 88. 5 8. 0 D0. Laurylamine, 90 Ethoxylated Stearylamide,10 88.5 0.5 Do. Do do 88.5 8. 0 Do. octadecylamine, 90..-. EthoxylatedTallow Amide, 10.... 88.5 0. 5 Do. Do do 88.5 8. 0 Fair.

l The mixed amine employed in Tables 1 and 2 comprised 25% docosylamine(C22), 30% eicosylamine (C20) 30% octadecylamine (C18), 13%hexadecylamine (C16), and 2% tetradecylamine (C Table 2 below,demonstrates the effect of the ethylene oxide content of the emulsifier:

condensate containing said amine and said amide in a quantity adequateto inhibit said corrosion.

1 The mixed amine employed in Table 1 was used throughout thedeterminations of Table 2.

It is believed that Table 2 indicates the necessity for an emulsifierhaving a relatively high ethylene oxide content, whereas additionalstudies have indicated the necessity for an ethylene oxide content ofbetween 70' to 98 percent.

It should also be noted that poor emulsions were achieved withemulsifiers having a carbon chain length of less than 10 carbon atoms.

It will be evident that by the present invention fatty monoamines can beeasily and readily introduced into the steam and/or steam condensate ofboiler systems at a relatively low cost, without experiencing thedifficulties and detects realized with amines alone, soluble aminesalts, or amines emulsified with compositions other than those of theinvention. For example, aqueous dispersions having a high amine contentand a low emulsifier content, may be obtained. Furthermore, aqueousemulsions of solid amines, which are readily dispersible in boilersystems, and which do not melt at temperatures significantly below themelting point of the amine, can be prepared. Conseqeuntly, thesecorrosion inhibitors may be distributed within the system to beprotected in the form of solids, to provide an excellent protective filmupon metal surfaces. This aspect presents obvious packaging benefits.

It is also apparent that various alternatives, substitutions andmodifications may be made in the present invention without departingfrom the reasonable spirit and scope of the inventions as defined by thefollowing claims:

I claim:

1. A method for inhibiting the corrosion of the surfaces of metalcomponents of a boiler system which are contacted by the steam andcondensate contained by the system, comprising dispersing within saidsteam and condensate an aqueous dispersion of a straight chain aliphatichydrocarbon primary amine in which said straight chain has a length ofbetween 10 to 24 carbon atoms, and an ethoxylated amide having theformula in which R is an aliphatic hydrocarbon radical having between 10to 24 carbon atoms, and x and y are integers having a total. value suchthat the ethyleneoxy content of said amide is between 70 to 98 percentby weight in which said aqueous dispersion contains at least 1 part byweight of said amide for each 99 parts by weight of said amine, andcontacting said surfaces with said steam and 2. A method as claimed byclaim 1 in which said amine is octadecylamine.

3. A method as claimed in claim 1 in which said amide is ethoxylatedoctadecylamide.

4. A method as claimed by claim 1 in which said amine is present in aquantity of between 40 to 99 parts by weight and said amide is presentin a quantity of between 1 to 60 parts by weight.

5. A method as claimed in claim 1 in which said aqueous dispersioncontains no more than percent by weight of said amine and said amide.

6. A corrosion inhibiting composition for boiler systems, consistingessentially of an aqueous dispersion of a straight chain aliphatichydrocarbon primary amine in which said straight chain has a length ofbetween 10 to 24 carbon atoms, and an ethoxylated amide having theformula (ozmomr in which R is an aliphatic hydrocarbon radical havingbetween 10 to 24 carbon atoms, and x and y are integers having a totalvalue such that the ethyleneoxy content of said amide is between 70 to98 percent by weight, in which said aqeuous dispersion contains at least1 part by weight of said amide for each 99 parts by weight of saidamine.

7. A composition as claimed in claim 6 in which said amide isoctadecylamide.

8. A composition as claimed in claim 6 in which said amine is present ina quantity of between 40 to 99' parts by weight and said amide ispresent in a quantity of between 1 to parts by weight.

9. A composition as claimed in claim 6 in which said aqueous dispersioncontains no more than 50 percent by weight of said amine and said amide.

References Cited UNITED STATES PATENTS 2,085,706 6/1937 Schoeller et'al. 260-124 2,956,889 10/1960 Denman 252-392 X LEON D. ROSDOL, PrimaryExaminer.

J. GLUCK, Assistant Examiner.

US. Cl. X.R.

